Review page language attributes so HTML and XML readers receive consistent language information. Check matching lang and xml:lang values, validate language codes, and recommend keeping both attributes for XHTML or removing the unnecessary XML attribute from standard HTML5.
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Use when applies to XHTML documents and polyglot HTML documents that must parse correctly as both HTML5 and XML. For modern HTML5-only documents, only `lang` is needed and `xml:lang` is not required. Check when auditing documents served as application/xhtml+xml or documents that include both attributes.
安装前可以查看交给 AI 代理的指令内容。
Screen readers use the lang attribute to select the correct voice profile and pronunciation engine. If lang and xml:lang disagree, XML-based processors (including some EPUB readers and older assistive technologies) may use xml:lang and get a different language than intended — causing text to be read aloud in the wrong language. For example, French text read with an English voice profile produces unintelligible output for French-speaking blind users.
lang and xml:lang are present on <html>, their values must be identicalxml:lang is only needed for XHTML or polyglot documents (valid as both HTML and XML)lang is required — xml:lang is redundanten, en-US, fr, zh-Hant)Inspect the <html> element for both lang and xml:lang attributes. If both are present, verify their values are identical (including subtags — en vs en-US is a mismatch). Also verify that the value is a valid BCP 47 language tag. Flag if the values differ in any way.
If lang and xml:lang are present but differ: update both to the same valid BCP 47 language code matching the primary language of the document content. If this is a standard HTML5 document (served as text/html), remove xml:lang — it is unnecessary. If this is XHTML or a polyglot document, keep both and ensure they are identical.
WCAG 2.1 SC 3.1.1 requires that the default human language of each web page can be programmatically determined. The lang attribute on <html> serves this purpose for HTML parsers. The xml:lang attribute serves the same purpose for XML parsers. When a document must be valid as both HTML and XML (polyglot), both attributes must be present and identical. A mismatch means the document claims different languages depending on which parser reads it, which can cause screen readers, translation tools, and spell checkers to use wrong language rules.
Review the rendered markup and interactive states that affect Match lang and xml:lang attributes. Flag exact elements, roles, labels, focus behavior, or keyboard interactions that violate the rule, and note how to verify the fix with browser accessibility tooling or assistive tech.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/accessibility/html-xml-lang-mismatch
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Create and review custom 404 pages that help visitors recover from broken or moved links through search and navigation. Check the rendered page and HTTP response so missing content returns a proper 404 status.
中文简介正在准备中。当前显示英语简介。
Audit or create a dedicated About page that explains a website’s purpose and identifies its people or organization. Review the rendered output and supporting information, including expertise and contact details, to find gaps.
中文简介正在准备中。当前显示英语简介。
Review and add automated accessibility checks for components, pages, and continuous integration workflows. Use axe-based tools to detect structural and attribute issues, while identifying checks that still need keyboard or screen reader testing.
中文简介正在准备中。当前显示英语简介。
Review sign-in, registration, multi-factor authentication, and account recovery for accessibility barriers. Find blocked paste, difficult code entry, and inaccessible backup methods, then suggest authentication paths that support password managers, autofill, or device approval.
中文简介正在准备中。当前显示英语简介。
Review form errors, success messages, and live updates so screen reader users receive important notifications. Check the HTML delivered to the browser, announcement settings, display duration, and dismissal controls, then identify specific elements that need changes.
中文简介正在准备中。当前显示英语简介。
Review HTML tables so screen reader users can understand how headers and data relate. Check header markup, table descriptions, and merged cells, then identify specific fixes and ways to verify them.
中文简介正在准备中。当前显示英语简介。